I own an ASUS N551ZU laptop (i have included the stats below). The laptop comes with a primary AMD Radeon(TM) R7 Graphic linked with a AMD Radeon R9 M280X but recently it won't switch to R9 from R7 while gaming as it is supposed to do. so in a game for example Assassin's Creed: Syndicate when i go to graphics setting section it shows that the game is using R7 instead of R9 so i have 1GB of video memory instead of 4GB and as far as i can remember it always used R9 in the past.

i have tried clean installing the Radeon drivers but it didn't fix the problem and i don't know what else i can do. I'm so frustrated. Does someone know how to fix this problem ?